Vertically polarized antenna



July 31, 1956 M. w. SCHELDORF VERTICALLY POLARIZED ANTENNA Filed March8, 1951 W a 1 7 M 2,751,311- 1 VERTICALLY POLARIZED ANTENNA Marvel w.-Scheldorf, Palos Heights, nl.,- assignor to Andrew Corporation; acorporation of Illinois Application March 8, 1951, steam. 214,537

sclaims. 01. 343-905) The present invention relates to a verticallypolarized antenna, and more particularly to such an antenna adaptedfor'VHF operation.

In the past it has been common to provide vertical polarization byantennas of the coaxial type. Particularly for mobile communicationservice it has been customary to stack concentric cylinders over asupporting mast structure. In the past it has been found'that' attimes'coaxial antennas did not produce the transmission characteristicsdesired. It has also been found that the ground plane antenna likewiseat times did not produce the desired transmission characteristics.

The coaxial antenna in one form consistsof a vertieal quarterwave-length extension of the inner conductorof the transmission lineplus a quarter wave-length cylinder over the outer conductor of thatline connected at the upper end and free at the bottom to form what iscommonly known as a skirt. I

The ground-plane antenna consisting of a vertical quarter wave-lengthextension of the inner conductor of the transmission line and a halfwave-length diameter ground plane fastened to'the end of the outerconductor of that line in a horizontal plane is not susceptible ofmodification to employ stacking. A number of attempts have been made tosolve the vertically polarized stacking problem. It would seem that thepredominant cause for their failure is that they employ the concentriccylinder prin ciple. These cylinders must have'considerable clearancefro'mthe mast for electrical isolation, and hence presentlargewindloading areas. Thisrequires a large mast diameter, which is bulky andconsequently the entire assembly is unreasonably bulky. Such anarrangement furthermore'requires feed hnes to be brought up through'themast" which makes service of the junctions diflicult or'impos sible."

It-has' been found that one of themost annoying difiiculties of both theground plane antenna and coaxial antennas 'is the tendency to couplepower to the mast, with corresponding sensitivity to surrounding objectsand height above the-ground. It, therefore, would be desirable toprovide an improved antenna structure not subject to certain of thesedifii'culties.

It is, therefore, an object of the present invention to provide animproved vertically polarized antenna having a substantially circularhorizontal pattern.

A further object of the present invention is to provide an improvedvertically polarized antenna having a high power gain. p

Still another objeet of the present invention is to provide a'n'improvedvertically polarized antenna which has negligible" coupling to thesupporting mast. U 7

A still further object of'the present inventionfis to provideanimp'roved antenna requiring'a minimumnumber of 'feedpdin'ts; I

Still'anoth'er object of the present invention is to provide avertically polarized antenna having a minimum wind load.

Other and further objects of the present invention sub- Patented July31, 1956 sequently will become apparent by reference to the followingdescription'taken in conjunction with theacconipanying drawing wherein:

Figure l is a representation of an'antenna constructed in accordancewith the principles of the present invention;

Figure rangement for providing a minimum number of feed points for theradiating elements shown in the antenna of Figure 1;

Figure 3 is a side view of one of the radiating elements; Figure 4 is adiagrammatic top view of the antenna" arrangement illustrated in Figure1; and

Figures 5 and 6 are graphical representations illustrat ing certainradiation characteristic patterns of 'the antenna. In Figure 1 there isshown a supportingmast l lwhich carries a plurality of radiatingelements 12 through 19' arranged in equal numbers on opposite sides ofthe mast'll' in a stepped or staggered relation. Each of the radiatingelements 12 to 19 is a fomed dipolei In the development of this antennait was found that a single folded dipole radiating element mounted on a'mastwas comparatively free from coupling to the mast, but'did'n'ot in ofitself provide 'a circular horizontal radiation pattern. The use of apair of dipole elements arranged on opposite sides of the mast provided'anarrangethe various'forms'of coaxial antennas. Froinan arrangementemploying two folded dipole elements on a mast therena'tura'lly wasdeveloped a folded dipole element array of the stacked varietyillustrated in Figure 1.

In order such as'shown' in Figure 1, thereis arrangementdiagrammatically represented in Figure 2.

to any" appreciable extent;

junetion of each pair. the dipoles line 21 at its upper extremityis'connected to thedipole element 12.

dipoleelement 16 (.932 being the relative velocity of propagation intransmission line 21). From thatjunction to the junctionco'nnected tothedipole'element 13"the" distance is 1.068 half wave-length. The distancefrom the'jun'ction to element 13 to the dipole element 17 again is .932half wave-length. A similar junction vertical transmission line'22interconnects the dipole elements 14, 15,

18 and 19. The two vertical junction transniission'lines 21 and 22 areinterconnected by a spiral junction trans mission hne 23 arranged on theother side of the mast.

The center or the spiral section 23 is connected to the" mainfeed'transm'ission line' 24"which is on the'same side of the mast. Inone embodiment the two vertical junc-' tion transmission lines, such asthe transmission-lines 21 and 2.2,had an impedance value of 51.5 ohms.The's'pifal junction transmission line had an impedance'value of' 63.8ohms which was joined to the main feed transmission line having animpedance of 5 1.5 ohms. Thus at each T junction there is a'o'ne totwo'impedance'transformer so that standing wave ratios in the feedtransmission lines arethe same as for the linesbeing fed. Thearrangement illustrated in Figure 2 has the advantage of keeping themain feed transmission line and spiral junctiontransmission line awayfrom the elements thereby to preve'ntu'ribalances and'disturbancesiiithe radiation pattern.- 7 Such" an arrangement furthermore hascertain physical advantages in that there is no obstruction to the endseal units, which support the dipole elements, and the junction with 2is a diagrammatic representation of an ark ment produc'ingthe desiredcircular horizontal p'atternj without many of the disadvantagesencountered in other types of antennas, such as the 'grou'nd'planeantenna" and to supply energy toastacke'darrangement,

employed aharness At a distance 's'uchas' .932 half I wave-length thereis provided a junction which is connected tothe' 3 the main feedtransmission line is at a position where the line is easily brought downthe rnast.

Figure 3 illustrates one of the dipole radiating elements which isformed of a plurality of rods or tubes 26, 27 and 28. The rod 27 isconnected to the rod 26 at one end by a strap or bar 29. The other rod28 is connected to the rod 26 by a strap or bar 31. One of the rods suchas the rod 27 at its other end is connected to a conductive member 32which engages a stud 33 arranged coaxially in an insulator 34. Theinsulator 34 is partially surrounded by a shield 35 connected to one endof the dipole rod 28.

If the elements shown in Figure 3 when mounted on a mast 11 such asshown in Figure l, were viewed from the top of the trust, thearrangement would be similar to that shown in Figure 4. In that figurethe top of the mast 11 is shown as being a large circle. Tangent to themast are a plurality of'shields and insulating members 35 carrying attheir outer extremities the dipole elements which include the rods 26and 27. The dipole elements are connected through the conductive studs33 to the harness arrangement shown in Figure 2. This isdiagrammatically represented in Figure 4 by the application of thereference character 21 to the line element extending between four dipolesupporting assemblies.

In Figure 5 there is shown a horizontal radiation pattern which isrepresentative of patterns obtained over a band of frequencies from 148to 162 megacycles. In the center of this diagram there is represented bya cross hatched circle the support mast 11 which carries the verticalfeed line 24 and has radiating .dipole elements arranged on oppositesides of the mast 11.

Figure 6 shows the radiation pattern of the antenna in the plane of thefeed line.

The resultant antenna structure is one in which there is no substantialcoupling to the mast. This is true in the stacked or array arrangementshown in Figure 1, and in the arrangement employing only two radiatingelements mounted on opposite sides of the support mast. The centralsupport structure, however, has one other advantage. It provides avertical polarized antenna which readily permits mounting a beacon oranother antenna above it. Likewise a lightning rod may be added to thetop of the antenna support without disturbing the operation of theantenna.

While at the present time no completely satisfactory explanation for theisolation of the antenna has been developed,it may be assumed that thefact that heavy standing waves of transmission line current in thefolded ends of the elements, oppose one another, the mast current isconsequently low. The specific structure described, does not require areturn path for transmission line currents, such as are found necessaryin all other arrangements. The radiation currents in the elements areadditive at the folded ends but the magnitudes relatively approach zero,so there would be little coupling from this portion of the element.

While for the purpose of illustrating and describing the presentinvention a certain preferred embodiment has been shown in the drawing,it is to be understood that the invention is not to be limited thereby,since such variations in the physical embodiment are contemplated as maybe commensurate with the spirit and scope of the invention set forth inthe accompanying claims.

I claim as "my invention:

1. A multi-element antenna comprising a mast supportingan even number offolded dipole elements intwo vertical planes, said elements beinglocated on opposite sides of said mast in staggered relation to eachother and in close proximity to said mast, and a coaxial transmissionline extending upwardly along said mast, a plurality of verticaltransmission lines extending along said mast and each being connected toone half of said dipole elements,

4 and a sinuous transmission line extending between said verticaltransmission lines and said first transmission line.

2. A multi-element antenna comprising a mast supporting an even numberof folded dipole elements in two vertical planes, said elements beinglocated on opposite sides of said mast in staggered linear relation toeach other and in close proximity to said mast, and a coaxialtransmission line extending upward along and behind said mast, aplurality of vertical transmission lines extending along the front ofsaid mast, each of said vertical transmission lines being connected tocertain dipole elements on opposite sides of said mast, each of saidverticaltransmission lines havin'g junctions for pairs of said dipoleelements at half wave length distance, and a sinuous coaxialtransmission line extending between said vertical transmission lines andsaid first transmission line.

3. A multi-element antenna comprising a mast supporting an even numberof folded dipole elements, said elements being located on opposite sidesof said mast in staggered linear relation to each other, a coaxialtransmission line extending upwardly along said mast, a plurality ofcoaxial vertical transmission lines extending along said mast and eachbeing connected to one-half of said 'dipol'e elements, each of saiddipole elements having one endconnected to the inner conductor of saidcoaxial tra'nsmis-:

sio'n line and the other end connected to the outer conductor of saidcoaxial transmission line, and 'a sinuous transmission line extendingbetween said vertical transmission lines and said firs t transmissionline.

4. A multi-element antenna comprising a mast supporting aneven number ofdipole elements in two vertical planes, said elements being located onopposite sides of said mast in staggered relation to each other and inclose proximity to said mast, each dipole having *one element thereofconnected to ground, and a coaxial transmission line extendingu'pwardlyalong said mast, a plurality of vertical transmission lines"extending along said mast and each being connected to one-half of saiddipole elements, and a sinuous transmission line extending between saidvertical transmission lines and 'said first transmission line, saidfirst coaxial transmission line and said plurality of verticaltransmission lines 'having like impedance characteristic values.

5. A multi-element antenna comprising a vertical mast supporting an evennumber-of dipole elements in two vettical planes located on oppositesides of said mast, said"'elements being arranged in staggered linearrelation to'each other and in close proximity to said mast, each dipoleelement having oneelement thereof connected to ground,

and 'a coaxial transmission liue extending along and behind said mast,"aplura'lity of vertical transmission lines extending along the front ofsaid mast, each of said vertical transmission lines being connected tocertain 'dipole elements on opposite sides of said mast, said firstcoaxial transmission line and said plurality of vertical transmissionlines having like characteristic impedance values, each of said verticaltransmission lines having junctions for pairs of said dipole'elements at-'half wave length distance, and a sinuous coaxial transmission lineextending between said vertical transmission 'lines and said firsttransmission line.

References Cited in the file of this patent UNITED STATES PATENTS2,080,577 Ponte May 18, 1 937 12,160,053 Barbour Ma 30, 1939 2,199,635Koch May 7, 1940 2,217,321 Runge et al Oct.f8, 1940 2,234,744 ThomasMar. 11, 1941 2,286,179 Lindenblad June 9, 1 942 2,512,,5 1-1 WeightonJune 20, 1950

